A number of reactions involving bulky transition states or large molecules cannot be carried out using commercially available aluminosilicate zeolites, since the critical pore diameter of these aluminosilicate zeolites does not allow the facile ingress and egress of such molecules. As a result, reactions involving particularly bulky transition states or large molecules are often conducted using environmentally undesirable catalysts, such as chlorided alumina or liquid-phase acids, such as sulfuric acid.
A large-pore silica, 14-membered ring, molecular sieve was described for the first time by K. J. Balkus et al in "Synthesis and Characterization of UTD-1: A Novel Zeolite Molecular Sieve" in ACS Petroleum Chemicals Preprints, Volume 40, page 296 (1995), and "Molecular Sieve Synthesis Using Metallocenes as Structure Directing Agents" in Mat. Res. Soc. Symp. Proc., Volume 368, page 369 (1995). Specifically, this large-pore silica molecular sieve is identified as UTD-1, a 14-membered ring, all-silica molecular sieve. UTD-1 is disclosed in U.S. Pat. No. 5,489,424.
In the article "Molecular Sieve Synthesis Using Metallocenes as Structure Directing Agents", K. J. Balkus, Jr. et al suggest incorporating aluminum into UTD-1 in an amount such that the Si/Al ratio is greater than 350 (corresponding to a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of greater than 700), to enhance the catalytic activity of UTD-1. However, the reference fails to describe or suggest the incorporation of greater amounts of alumina or the method by which aluminum is incorporated into the molecular sieve framework. To date, the synthesis of a large-pore, 14-membered ring, true aluminosilicate molecular sieve, namely a zeolite comprising alumina and silica, has not been reported.
The article further indicates that crystals of the UTD-1 silica molecular sieve are large "bundles of two dimensional planks . . . about 2 microns across."